Added MultipleDeck which can be used in place of the old QuadDeck, converted cards from classes to records as it is useful to have default equality checks.

src/Nadeko.Econ/Deck/Regular/MultipleRegularDeck/MultipleRegularDeck.cs

@@ -0,0 +1,28 @@
+namespace Nadeko.Econ;
+
+public class MultipleRegularDeck : NewDeck<RegularCard, RegularSuit, RegularValue>
+{
+    private int Decks { get; }
+
+    public override int TotalCount { get; }
+
+    public MultipleRegularDeck(int decks = 1)
+    {
+        if (decks < 1)
+            throw new ArgumentOutOfRangeException(nameof(decks), "Has to be more than 0");
+
+        Decks = decks;
+        TotalCount = base.TotalCount * decks;
+        
+        for (var i = 0; i < Decks; i++)
+        {
+            foreach (var suit in _suits)
+            {
+                foreach (var val in _values)
+                {
+                    _cards.AddLast((RegularCard)Activator.CreateInstance(typeof(RegularCard), suit, val)!);
+                }
+            }
+        }
+    }
+}